Title  The three-dimensional water cycle of Mars
Pi     E. Lellouch
Time   320 hrs

1. Name of program and authors
Title: The three-dimensional water cycle of Mars
Authors: E. Lellouch

2. One short paragraph with science goal(s)
Abstract: The water cycle on Mars is a key subject in
   martian research and a focus of space missions to Mars.
   As compared to space missions, the great interest
   of ALMA will be the possibility to determine the vertical
   profile of water (through H2O, H2O18, and HDO), i.e. to retrieve true
   3-D fields of water, and their variability with season. 
   The ultimate goal is the understanding of exchanges and interactions 
   between the atmosphere and the sources of water (regolith, polar caps).
   Spatial variations in the D/H ratio will also be searched for. 

3. Number of sources : 1
   
   Mars

4. Coordinates:

4.1. Rough RA and DEC 

     Variable

4.2. Moving target: yes/no (e.g. comet, planet, ...)

	Yes

4.3. Time critical: yes/no (e.g. SN, GRB, ...)

	Yes. Needs to be done at several Mars seasons

4.4. Scheduling constraints: (optional)


5. Spatial scales:

5.1. Angular resolution (arcsec): 0.2-0.5

5.2. Range of spatial scales/FOV (arcsec):  FOV = 2-20

     (optional: indicate whether single-field, small mosaic,
     wide-field mosaic...)

5.3. Required pointing accuracy: (arcsec) 0.2


6. Observational setup

6.1. Single dish total power data: required

     Observing modes for single dish total power: wobbler switch

     (e.g., nutator switch; frequency switch; position switch;
     on-the-fly mapping; and combinations of the above)
	

6.2. Stand-alone ACA: no

6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: 
     required

6.4. Subarrays of 12m baseline-ALMA antennas: no


7. Frequencies:

7.1. Receiver band: Band 5, 6, 7, 8
7.2. Lines and Frequencies (GHz): 

	H2O 183 or 325 GHz
	HDO 226, 242, 464 GHz
	H2O18 at 204 GHz (e.g.) 
     
7.3. Spectral resolution (km/s): 1

7.4. Bandwidth or spectral coverage (km/s or GHz): 0.5 GHz for HDO and H2O18
8 GHz for H2O.

8. Continuum flux density:

8.1. Typical value (Jy):

	Mars  : 200 K

8.2. Required continuum rms (Jy or K): 0.1 K

8.3. Dynamic range within image:

     (from 7.1 and 7.2, but also indicate whether, e.g., weak objects
     next to bright objects)

8.4. Calibration requirements: absolute      ( 10% )
                               repeatability ( 10% )
                               relative      ( 10% )


9. Line intensity:

9.1. Typical value (K or Jy): 2 K (HDO and H2O18) - 100 K (H2O) 
    
9.2. Required rms per channel (K or Jy): 0.1 K

9.3. Spectral dynamic range:

9.4. Calibration requirements: absolute      ( 10% )
                               repeatability ( 10% )
                               relative      ( 10% )

10. Polarization: no

10.1. Required Stokes parameters:

10.2. Total polarized flux density (Jy):

10.3. Required polarization rms and/or dynamic range:

10.4. Polarization fidelity:

10.5. Required calibration accuracy:


11. Integration time for each observing mode/receiver setting (hr):

2 hr - 40 h per line, depending on Mars' size. Observations should be performed at
least at four Mars seasons

12. Total integration time for program (hr):

~ 320 hours (4 seasons x 4 lines x 20 hours in average)

13. Comments on observing strategy : For Mars, should be combined with DRSP 4.1.1. because temperature profile
is needed to retrieve water vapor and with DRSP 4.1.3 to search for correlations between water and other
minor species.
--------------------------------------------------
Review v2.0:
 
Review 4.1.1-4.1.8

The only question I have with regards to these projects is the use of
ACA cross-correlated with ALMA-12m. Several projects list this option
as 'required' or as 'beneficial', but no arguments are given. 

- When listed as 'required' does this mean that the observations are
  mosaics, and that the ACA is needed to provide the intermediate
  scales? If so, are the cross-correlations with the ALMA-12m antennas
  needed, or could simultaneous ACA-7m-only observations also suffice?

- When listed as 'beneficial' is this purely for S/N reasons or also
  for uv-coverage? The cross-correlation option is fairly demanding on
  the scheduling, and unlikely to be used unless absolutely necessary.